Metamaterials Based Mechanically Adaptive Scaffolds for Cells

Cells are known to have an active participation in shaping their environment. It has been shown that there is a two-way communication between cells and the scaffold/extra-cellular matrix. It is well established that cells respond to the stiffness of their surrounding matrix. For example cell differentiation and morphology are impacted based on the substrate stiffness. It has been shown how geometry and topographical features have an impact. Different tissues also show diverse mechanical behaviour depending on their functions. However, most of the approaches have been towards manipulation of cells via either chemical modification of surfaces or static 3D patterns. Majority of the research discussing these aspects with reference to cell behaviour have a major disconnect in term of the scale at which the scaffolds or the investigated features are fabricated. In most studies in the past the feature sizes have been at least an order of magnitude larger than the cells. With currently present advances in additive manufacturing technology as well as implementation of design concepts from metamaterial designs, this gap can be narrowed. With techniques like two-photon polymerization-based printing combined with mechanical meta-materials like auxetics we can achieve scaffolds that have geometrical features that are relevant to individual cells (1-5 µm) and with tuneable mechanical responses as well as the surface area available for cells to adhere to.<br/>The aim of this project is to design and fabricate structures which can be actively deformed by traction forces applied by cells. To achieve a cell induced deformation of 3D printed structures, an auxetic design called the snakeskin kirigami pattern is selected as the principle design to build up on. The advantage with a design-based approach is that we do not rely on material chemistry. The mechanics and the deformation profile of the scaffold can be tuned by changing the geometrical aspects. Herein, 3D scaffolds based on snakeskin kirigami pattern were designed and fabricated via two-photon polymerization-based printing. Mechanical characterization of the 2D patterns on different scales (mm & µm) show ~90% drop in effective Young’s modulus in comparison to the bulk material. Preliminary cell experiments show a bioactive micro-scaffold with active deformation in the structure post cell seeding.